Adds ArcanistJSHintLinter to check JS files for errors and potential problems.

This patch adds ArcanistJSHintLinter class and three new .arcconfig options:

 * lint.jshint.prefix - directory where JSHint binary resides
 * lint.jshint.bin - JSHint binary name (if different from 'jshint')
 * lint.jshint.config - a JSON file with JSHint project-wide options

By default, this linter assumes that JSHint is installed on user's system
as an NPM package.

Test Plan:

(1)

Run `npm install jshint -g` to install JSHint and add
ArcanistJSHintLinter to your Lint Engine (I didn't see PEP8 or
PyFlakes in the PhutilLintEngine so I decided to not to put
JSHint in there). After that you can do `arc lint my.js`.

(2)

Create a new file, config.json, and add `{ "white": true }` in it.
Add `"lint.jshint.config": "/path/to/config.json"` to your .arcconfig and
run `arc lint my.js`. After that, unless your name is Douglas Crockford,
you'll see tons of JSHint warnings about minor PEP8-like things (spacing, etc.)

src/__phutil_library_map__.php

@@ -46,6 +46,7 @@ phutil_register_library_map(array(
     'ArcanistHelpWorkflow' => 'workflow/help',
     'ArcanistHookAPI' => 'repository/hookapi/base',
     'ArcanistInstallCertificateWorkflow' => 'workflow/install-certificate',
+    'ArcanistJSHintLinter' => 'lint/linter/jshint',
     'ArcanistLiberateLintEngine' => 'lint/engine/liberate',
     'ArcanistLiberateWorkflow' => 'workflow/liberate',
     'ArcanistLicenseLinter' => 'lint/linter/license',
@@ -127,6 +128,7 @@ phutil_register_library_map(array(
     'ArcanistGitHookPreReceiveWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistHelpWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistInstallCertificateWorkflow' => 'ArcanistBaseWorkflow',
+    'ArcanistJSHintLinter' => 'ArcanistLinter',
     'ArcanistLiberateLintEngine' => 'ArcanistLintEngine',
     'ArcanistLiberateWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistLicenseLinter' => 'ArcanistLinter',

src/lint/linter/jshint/ArcanistJSHintLinter.php

@@ -0,0 +1,170 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Uses "JSHint" to detect errors and potential problems in JavaScript code.
+ * To use this linter, you must install jshint through NPM (Node Package
+ * Manager). You can configure different JSHint options on a per-file basis.
+ *
+ * If you have NodeJS installed you should be able to install jshint with
+ * ##npm install jshint -g## (don't forget the -g flag or NPM will install
+ * the package locally). If your system is unusual, you can manually specify
+ * the location of jshint and its dependencies by configuring these keys in
+ * your .arcconfig:
+ *
+ *   lint.jshint.prefix
+ *   lint.jshint.bin
+ *
+ * If you want to configure custom options for your project, create a JSON
+ * file with these options and add the path to the file to your .arcconfig
+ * by configuring this key:
+ *
+ *   lint.jshint.config
+ *
+ * Example JSON file (config.json):
+ *
+ * {
+ *     "predef": [    // Custom globals
+ *       "myGlobalVariable",
+ *       "anotherGlobalVariable"
+ *     ],
+ *
+ *     "es5": true,   // Allow ES5 syntax
+ *     "strict": true // Require strict mode
+ * }
+ *
+ * For more options see http://www.jshint.com/options/.
+ *
+ * @group linter
+ */
+class ArcanistJSHintLinter extends ArcanistLinter {
+
+  const JSHINT_ERROR = 1;
+
+  public function getLinterName() {
+    return 'JSHint';
+  }
+
+  public function getLintSeverityMap() {
+    return array(
+      self::JSHINT_ERROR => ArcanistLintSeverity::SEVERITY_ERROR
+    );
+  }
+
+  public function getLintNameMap() {
+    return array(
+      self::JSHINT_ERROR => "JSHint Error"
+    );
+  }
+
+  public function getJSHintOptions() {
+    $working_copy = $this->getEngine()->getWorkingCopy();
+    $options = '--reporter '.dirname(realpath(__FILE__)).'/reporter.js';
+    $config = $working_copy->getConfig('lint.jshint.config');
+
+    if ($config !== null) {
+      $config = Filesystem::resolvePath($config, $working_copy->getProjectRoot());
+
+      if (!Filesystem::pathExists($config)) {
+        throw new ArcanistUsageException(
+          "Unable to find custom options file defined by 'lint.jshint.config'. ".
+          "Make sure that the path is correct.");
+      }
+
+      $options .= ' --config '.$config;
+    }
+
+    return $options;
+  }
+
+  private function getJSHintPath() {
+    $working_copy = $this->getEngine()->getWorkingCopy();
+    $prefix = $working_copy->getConfig('lint.jshint.prefix');
+    $bin = $working_copy->getConfig('lint.jshint.bin');
+
+    if ($bin === null) {
+      $bin = "jshint";
+    }
+
+    if ($prefix !== null) {
+      $bin = $prefix."/".$bin;
+
+      if (!Filesystem::pathExists($bin)) {
+        throw new ArcanistUsageException(
+          "Unable to find JSHint binary in a specified directory. Make sure ".
+          "that 'lint.jshint.prefix' and 'lint.jshint.bin' keys are set ".
+          "correctly. If you'd rather use a copy of JSHint installed globally, ".
+          "you can just remove these keys from your .arcconfig");
+      }
+
+      return $bin;
+    }
+
+    // Look for globally installed JSHint
+    list($err) = exec_manual('which %s', $bin);
+    if ($err) {
+      throw new ArcanistUsageException(
+        "JSHint does not appear to be installed on this system. Install it ".
+        "(e.g., with 'npm install jshint -g') or configure ".
+        "'lint.jshint.prefix' in your .arcconfig to point to the directory ".
+        "where it resides.");
+    }
+
+    return $bin;
+  }
+
+  public function willLintPaths(array $paths) {
+    $jshint_bin = $this->getJSHintPath();
+    $jshint_options = $this->getJSHintOptions();
+    $futures = array();
+
+    foreach ($paths as $path) {
+      $filepath = $this->getEngine()->getFilePathOnDisk($path);
+      $futures[$path] = new ExecFuture("{$jshint_bin} {$filepath} ${jshint_options}");
+    }
+
+    foreach (Futures($futures)->limit(8) as $path => $future) {
+      $this->results[$path] = $future->resolve();
+    }
+  }
+
+  public function lintPath($path) {
+    list($rc, $stdout) = $this->results[$path];
+
+    if ($rc === 0) {
+      return;
+    }
+
+    $errors = json_decode($stdout);
+    if (!is_array($errors)) {
+      // Something went wrong and we can't decode the output. Exit abnormally.
+      throw new ArcanistUsageException(
+        "JSHint returned output we can't parse. Check that your JSHint installation.\n".
+        "Output:\n".
+        $stdout);
+    }
+
+    foreach ($errors as $err) {
+      $this->raiseLintAtLine(
+        $err->line,
+        $err->col,
+        self::JSHINT_ERROR,
+        $err->reason);
+    }
+  }
+}

src/lint/linter/jshint/__init__.php

@@ -0,0 +1,16 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+phutil_require_module('arcanist', 'lint/linter/base');
+phutil_require_module('arcanist', 'lint/message');
+phutil_require_module('arcanist', 'lint/severity');
+
+phutil_require_module('phutil', 'future/exec');
+
+
+phutil_require_source('ArcanistJSHintLinter.php');

src/lint/linter/jshint/reporter.js

@@ -0,0 +1,18 @@
+module.exports = {
+    reporter: function (results) {
+        var report = [];
+
+        results.forEach(function (result) {
+            var error = result.error;
+
+            report.push({
+                'file': result.file,
+                'line': error.line,
+                'col': error.character,
+                'reason': error.reason
+            });
+        });
+
+        process.stdout.write(JSON.stringify(report));
+    }
+};